For the automatic development of a photographic image onto paper, there is available what is commonly known as a "developing minilab" which consists of a small, self-contained work station which has the capability of forming a latent image of desired size and orientation from a negative onto photographic paper. The minilab then chemically develops this latent image in permanent form onto the paper. The development of the latent image is typically accomplished in a number of individual chemical tanks located inside the minilab which contain developer, bleach-fix, and stabilizer. At the conclusion of the chemical processing, the photographic paper is automatically dried and then discharged from the machine for delivery to the customer.
In the chemical processing of the latent image, a number of process variables must be controlled within relatively small tolerances. For instance, the processing chemicals must be replenished and maintained as they are used up in the development of the latent image. As the fresh chemicals are added, it is important that they be evenly distributed throughout the solution so as to maintain a uniform concentration. Otherwise, concentration gradients can appear in the solution which cause the paper to become streaked during the developing process. It also is desirable that the contaminants formed during the developing process be removed. It is further desirable to control the level of processing chemicals in the bath in order to insure the photographic paper which is being transported through the bath is properly treated. It is also a desired feature to minimize the amount of oxygen introduced into the processing chemicals in order to prevent their oxidation. This requires that any turbulence of the chemicals during processing be minimized so as to minimize their aeration.
Conventionally, a number of photographic film processors have been disclosed. For example, in U.S. Pat. No. 4,268,156 by Kostiner there is described a washing apparatus for photographic materials wherein there is provided a tank having a lower system for introducing processing chemicals and an upper weir which forms a zone for removing the chemicals from the tank.
A liquid circulating system for photographic film processing is discussed by Gaskell in U.S. Pat. No. 3,922,702, wherein liquid circulation is achieved by removing the liquid from the upper part of the tank and then pumping it back in through an inlet distribution chamber in the bottom of the tank.
Otsu, in U.S. Pat. No. 4,312,585, discusses a system for treating photographic film in which a recirculating flow of treatment liquid is established over the film.
Furthermore, a treatment tank for photographic film is disclosed in U.S. Pat. No. 4,641,941 by Yoshimi, wherein the tank has a number of overflow devices for removing insoluble solids suspended in the treatment liquid.